WO 2011/054509 describes a method for manufacturing a multi-density shoe sole comprising repeated injections of sole material onto a shoe upper mounted on a last and placed in a mould. The method includes an insert placed in the mould prior to a first injection takes place through a sprue channel placed in the mould. After the first injected material has cured, the insert is removed and a second injection takes place through a second sprue channel placed in the mould. A drawback of this solution is that it always requires two injection channels placed in the mould, which makes the mould complicated and more expensive compared to a mould provided with only one channel. Furthermore, the method and the insert are not suitable for producing sole parts placed at the under-surface of the outsole and are not suitable for producing several shoe parts. Further, the method will induce a melt scar in a heel cap when the method is used for producing such a shoe part, due to the injection channel placed in the mould and the outlet corresponding to the visible back surface of the heel cap.
Therefore, it is an object of the invention to provide a method and an insert overcoming at least some of the disadvantages of the prior art or providing at least a useful alternative.